Gravity-type pipe conveyance systems for waste or storm water generally include a mainline pipe or conduit to which service lateral pipes are connected. Many applications call for the connection of the lateral pipes to be made such that the lateral is perpendicular to the mainline pipe. Such connections are often referred to as “Tee” connections or service connections. Alternatively, the service lateral pipe can be connected at an angle (although with the long axis intersecting the long axis of the mainline pipe) and is thus designated, for example, as a “Wye” or 45-Degree service connection.
Service connections require a hole to be cored through the sidewall of the mainline pipe. The diameter of the cored hole is made slightly larger than the diameter of the service lateral pipe, which has a smaller diameter than the mainline pipe.
One effective service connection system is available from Inserta Fittings Inc., the assignee of the present application (www.insertatee.com), and marketed under the trademark INSERTA FITTINGS. That system comprises a three-piece service connection that is compression fit, without special tooling, into the hole that is cored through the wall of a wastewater or storm water mainline pipe. The three-piece service connection comprises a substantially rigid, cylindrical, hollow hub; an elastomeric sleeve; and a stainless steel band. The sleeve fits into a cored hole in the mainline pipe. A leading end of the hub is forcibly inserted into the elastomeric sleeve. After the hub is inserted, a stainless steel band is fastened around the sleeve to secure together the sleeve and the hub. The exposed or trailing end of the hub can be shaped to define a conventional bell component of a bell and spigot joint, and receives the spigot end of the service lateral that is to be connected. This type of service connection may be used with any of a wide variety of pipe types (concrete, PVC, corrugated, etc).
It is important to control the depth of penetration of the hub into the mainline pipe when the service connection is made. Many municipalities specify that a high percentage of the mainline pipe must remain clear after installation of the lateral pipe so that normal flow through the pipe is not impeded, and so that there is provided sufficient clearance to permit passage of remote inspection devices through the mainline pipe past the service connections. One required way of inspecting for this is to have the installer pull a mandrel through the pipe and past the connection. The mandrel is specified to have an outside diameter that is 95% of the inside diameter of the mainline pipe.
If the hub were inserted too far into the mainline pipe, the amount of clearance in the mainline pipe could be reduced to an unsatisfactory level (thus impeding the movement of the inspection mandrel just noted). In this regard, it is possible for an installer to apply excessive axial force on the hub when inserting the hub into the sleeve. Alternatively, too much axial force may be applied to the service lateral pipe when fitting the spigot end of that pipe into the connection hub. In such an instance, the excessive force may cause the hub to move too far through the sleeve, and create an undesirable amount of penetration of the leading end of the hub into the mainline pipe, which, as noted, can result in interference with the operation and/or inspection of the mainline pipe.
The hub is forcibly inserted into the sleeve because the fit between the sleeve and hub is snug, and because of the high friction coefficient between the elastomeric sleeve and the hub. Currently, the leading ends of hubs are shaped to have external bevels that facilitate the insertion of the hub through the snug-fitting elastomeric sleeve.
In the past, hubs have been provided with visible markings on the exterior to serve as a hub insertion limit indicator. That is, a mark, such as a thick, red line, was placed on the hub and is normally visible to the installer. If the installer of the lateral pipe drove the hub into the sleeve by the correct amount, the marking line would remain at least partly visible, aligned with the outer edge of the sleeve into which the hub is inserted.
If, however, an installer drove the hub too far into the sleeve that is mounted to the mainline pipe (hence driving the hub too far into the mainline pipe) the line would not be visible, thus indicating the defective installation of the lateral pipe. In some construction environments, however, rainwater, mud, wear, and other elements may interfere with the installer's view of (hence use of) the limit marking on the hub, thus reducing or eliminating the usefulness of the mark.
In addition to minimizing the amount of penetration of the sleeved hub into the mainline pipe, it is also desirable to ensure that the service connection is adequately sealed. The sealing aspect of such connections is subject to increasingly rigorous testing, including air and/or water pressure and seismic testing, as part of an inspection approval process.
The present invention is directed to an improved lateral pipe connection assembly that minimizes the amount the penetration of the hub into the cored hole of the mainline pipe and that provides enhanced sealing of the connection.